Urgent: Can't found docs in shared Notebook

hi, I have shared the notebook (with sub-notebook and some docs) with others for View permission, however, just found that the users could see the name of the notebook and the sub-notebook ONLY, the docs inside the sub-notebook are gone! Even I have shared the notebook to someone with Manger permission, he can only see the notebook but not found any docs inside..... does anyone know what's the problem here?? Please kindly help~~~

Problems in "Notebook" (Anyone could help?)

User A (Notebook shared) -----> \ Common Info \ Sub-Notebook

1/ Anyone can see the pages under "Common Info"
2/ NO users with viewer permission could see the pages under "Sub-Notebook"

It's so strange of the Notebook sharing~ User A has shared his notebook "Common Info" and sub-notebook "Sub-Notebook" to group FIN with manager permission, and shared to group MKT with viewer permission (for both level). One day, the user in group FIN created a "page" under the shared notebook "Sub-Notebook", found that ONLY he can see the added page, others even the User A cannot see it~~~~ What's wrong in this case??

Also, the problem still exist - Users with Viewer Permission CANNOT see any pages under "Sub-Notebook", but can see the pages under "Common Info"....